This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-140272, filed May 12, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a heating apparatus used to heat a workpiece such as a wafer in a semiconductor manufacturing process, for example.
In a semiconductor manufacturing process, heating apparatuses for heating wafers, semiconductor materials, are used to subject the wafers to CVD (chemical vapor deposition), PVD (physical vapor deposition), or etching. Some of these known heating apparatuses not only heat the wafers but also function as electrostatic chucks.
For example, a heating apparatus for semiconductor manufacturing process described in Jpn. Pat. Appln. KOKOKU Publication No. 6-28258 or Jpn. Pat. No. 2525974 comprises a heater plate that has a resistance heating element embedded therein and is located in a chamber that is insulated from the outside air. The heater plate is supported in a given position in the chamber by means of a hollow (tubular) support member. If necessary, the heater plate may be provided with a thermocouple for temperature control or an electrode for an electrostatic chuck.
The resistance heating element embedded in the heater plate is connected to a lead wire. The lead wire is taken out from the back surface of the heater plate toward the support member, and is connected to a power supply outside the chamber through the interior of the support member. Electric wires for the thermocouple and the electrode for electrostatic chuck are also taken out from the back surface of the heater plate and drawn out of the chamber through the support member. Thus, according to this conventional arrangement, the hollow tubular support member is bonded directly to the back surface of the heater plate, and a joint between the two members is sealed to keep the interior of the chamber airtight. Accordingly, a part of the back surface of the heater plate is allowed to touch the atmosphere through the internal space of the support member.
In the case of the conventional heating apparatus described above, a part of the back surface of the heater plate touches the atmosphere through the internal space of the support member, so that some of heat from the heater plate is inevitably radiated to the atmosphere side through the internal space of the support member. Accordingly, the temperature of that part of the heater plate which touches the atmosphere locally lowers, so that the heater plate is subject to unevenness in temperature. Since the heater plate that is used to heat wafers in the semiconductor manufacturing process requires uniform temperature distribution, in particular, unevenness in temperature is a serious problem. If the heater plate is subject to unevenness in temperature, moreover, it is affected by a greater thermal stress than in the case where the temperature distribution is uniform, so that it may be deformed or broken.
One end of the support member is connected to the heater plate, while the other end is fixed to the wall of the chamber. Therefore, the one end of the support member that receives the heat from the heater plate is kept at a high temperature, and the other end at low temperature. If this temperature gradient is sharp, a great thermal stress is generated in the support member and the like, so that the support member itself or its mounting portion on the chamber wall may possibly break. Further, a current must be supplied to compensate for the quantity of heat that escapes through the back surface of the heater plate, and the power consumption increases correspondingly.
Conventionally, the heater plate and the support member are integral with each other. If the heater specifications change as the semiconductor manufacturing process is changed, for example, therefore, the whole heating apparatus including the support member as well as the heater plate must be replaced. If the heater plate requires replacement on account of disconnection or corrosion, moreover, not only the heater plate but also the whole heating apparatus must be replaced, which is uneconomical and time consuming.
Accordingly, the object of the present invention is to provide a heating apparatus designed so that a heater plate is less liable to unevenness in temperature, the temperature gradient of a support structure is lessened, and the heater plate can be easily replaced with a new one.
In order to achieve the above object, a heating apparatus according to the present invention comprises a heater plate having a surface for supporting a to-be-heated object and including a resistance heating element, first terminals protruding on the reverse side of the heater plate and connected electrically to the resistance heating element, a support structure for supporting the heater plate in a given position in a chamber, second terminals attached to the support structure, individually corresponding in position to the first terminals, and connected to an electric power supply for supplying electric power to the resistance heating element, and a joint member of an electrically-conductive material fitted on the first and second terminals, thereby connecting the first and second terminals electrically and mechanically to one another, and removably attached to at least one of the terminals.
Thus, according to the present invention, the heater plate and the support structure are separate components, and the terminals provided individually on these components are removably coupled to one another by means of the springy electrically-conductive joint member. By doing this, the heater plate and the support structure can be separated from each other. According to this invention, only the heater plate can be replaced with ease. Therefore, the maintenance costs and other costs of the heating apparatus can be reduced. Since the heater plate is supported indirectly on the support structure by means of the joint member, moreover, heat from the heater plate can be prevented from escaping through the support structure.
Accordingly, unevenness in the temperature of the heater plate is lessened, and the extra power consumed due to escaping heat can be reduced. Further, the quantity of heat the support structure receives from the heater plate is also reduced. Thus, the temperature gradient between that portion of the support structure which is situated near the heater plate and that portion which is fixed to the chamber can be eased, so that breakage of the support structure that is attributable to generation of thermal stress can be avoided.
Preferably, the support structure includes a top plate formed of an electrically-insulating, heat-resistant material (e.g., ceramic material) and having a diameter smaller than that of the heater plate and a stem provided on the reverse side of the top plate. The second terminals protrude from an end face of the top plate toward the heater plate. A thermal insulating space is defined between the end face of the top plate and the heater plate. According to this invention, materials can be used according to the respective functions of the heater plate and the support structure. In this case, the quantity of heat transmitted from the heater plate to the support structure side can be reduced further.
Preferably, in the present invention, the joint member is formed of a springy material and is removably fitted on the first or second terminals by utilizing its springiness. According to this invention, the joint member can be easily attached to and detached from the terminals utilizing its springiness.
In the present invention, the joint member may be a cylindrical spring having a slit, for example. The inside diameter of the cylindrical spring is smaller than the outside diameter of the first or second terminals so that the first or second terminals can be inserted into the cylindrical spring. According to this invention, the joint member is formed of the cylindrical spring that can be easily attached to and detached from the terminals.
In the present invention, the joint member may be a coil spring. The inside diameter of the cylindrical spring is smaller than the outside diameter of the first or second terminals so that the first or second terminals can be inserted into the cylindrical spring. According to this invention, the joint member is formed of the coil spring that can be easily attached to and detached from the terminals.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.